Referring to FIG. 1, there is shown a schematic view of a conventional passenger boarding bridge leveling mechanism. As shown in FIG. 1, the conventional passenger boarding bridge leveling mechanism 10 includes a drive device 11, a swing bar 12, a driving bar 13, a first detection switch 14, and a leveling wheel 15. The drive device 11 is mounted on a passenger boarding bridge 100 (see FIG. 2), one end of the swing bar 12 is hinged to the drive device 11, the other end of the swing bar 12 is hinged to one end of the driving bar 13, and the other end of the driving bar 13 mounts the first detection switch 14 and the leveling wheel 15. The first detection switch 14 may be, for example, a limit switch or an encoder, and the leveling wheel 15 may be a rubber wheel.
When the passenger boarding bridge 100 docks with an aircraft, the drive device 11 drives the swing bar 12 to drive the driving bar 13 to move the leveling wheel 15 in order to contact and maintain a certain pressure to press on an aircraft fuselage. When a passenger gets on/off the aircraft or loads/unloads the cargo, a body of the aircraft will ascend or descend. Due to a pressure between the leveling wheel 15 and the aircraft fuselage, the leveling wheel 15 will roll on the aircraft fuselage during the ascent or descent of the aircraft fuselage, and because the leveling wheel 15 is connected to the first detection switch 14, the first detection switch 14 may detect a signal of the leveling wheel 15 rotated relative to the driving bar 13, and provide the detected signal to a PLC, and the PLC calculates a distance of the ascent or descent of the aircraft fuselage according to the received signal. A front end of the passenger boarding bridge 100 is controlled to ascend or descend following the aircraft fuselage so that the passenger boarding bridge always maintains a suitable height position to dock with the aircraft fuselage.
Referring to FIG. 2, there is shown a comparison schematic diagram between the initial position of the passenger boarding bridge docking with the aircraft and the position of the passenger boarding bridge after it has ascended. As shown in FIG. 2, a rear end of the passenger boarding bridge 100 is hinged to a fixed building such as an airport terminal 200, and the passenger boarding bridge 100 may be extended back and forth, so that its front end can dock with the aircraft fuselage. As described above, the front end of the PLC controlled passenger boarding bridge 100 ascends or descends as the aircraft fuselage ascends or descends. However, the current structure of the passenger boarding bridge 100 determines that the front end of the passenger boarding bridge 100 will simultaneously be extended back and forth as it ascends or descends. As shown in FIG. 2, after the front end of the passenger boarding bridge 100 ascends, the passenger boarding bridge 100 moves a displacement ΔL in a horizontal direction compared with the initial position. Once the front end of the passenger boarding bridge 100 generates a horizontal displacement in the horizontal direction, a hinge point between the driving bar 13 and the swing bar 12 of the leveling mechanism will also move forward and backward, and the leveling wheel 15 of the leveling mechanism remains to be pressed against the aircraft fuselage. Thus, the forward and backward movement of the hinge point between the driving bar 13 and the swing bar 12 will make the leveling wheel 15 roll vertically on the aircraft fuselage, while the vertical rolling of the leveling wheel 15 means that the leveling wheel 15 is rotated relative to the driving bar 13. This relative rotation is detected by a detecting device mounted on the driving bar 13, thereby leading to a situation that the PLC misjudges the vertical motion of the aircraft fuselage and a detection error occurs.
Referring to FIG. 3, there is shown a schematic view of a detection error due to an angular change of the driving bar in the leveling mechanism. As shown in FIG. 3, the front end of the passenger boarding bridge 100 extends a displacement G in a horizontal direction, and in this process, one end of the driving bar 13 is changed from an initial position (see the solid line) to a position away from the aircraft (see the broken line) so as to generate an angular change α, and the other end of the driving bar 13 moves a displacement H in a vertical direction, which corresponds to a certain distance that the leveling wheel 15 vertically moves along the aircraft fuselage. Therefore, as a back and forth extension of the front end of the passenger boarding bridge 100 in the horizontal direction changes, the hinge point of the lower end of the driving bar 13 is brought to move back and forth, and the angle of the driving bar 13 relative to the leveling wheel 15 also changes accordingly, which change is detected by the detecting device mounted on the driving bar 13, thereby leading to a situation that the PLC misjudges that the aircraft fuselage moves vertically and a detection error occurs.
Referring to FIG. 4, there is shown a detection error curve of a conventional passenger boarding bridge leveling mechanism. It can be seen from FIG. 4 that, as a retraction distance of the front end of the passenger boarding bridge 100 increases (further and further away from the aircraft), the detection error curve caused by a change of the horizontal distance tends to rapidly rise, which means that the detection error caused by the change of the horizontal distance rapidly increases as the retraction distance of the front end of the passenger boarding bridge 100 increases; and simultaneously, as shown in FIG. 4, the detection error curve caused by the angular change of the driving bar 13 also presents an upwards tendency as the retraction distance of the front end of the passenger boarding bridge 100 increases, i.e., the detection error caused by the angular change of the driving bar 13 also gradually increases as the retraction distance of the front end of the passenger boarding bridge 100 increases, since a total detection error is a sum of the detection error caused by the change of horizontal distance and the detection error caused by the angular change, the total detection error rapidly increases as the retraction distance of the front end of the passenger boarding bridge 100 increases. Therefore, a passenger boarding bridge leveling mechanism currently causes a larger detection error with respect to the mechanical principle, thereby jeopardizing safety of the aircraft.
It can be determined according to the above analysis that, if the leveling wheel 15 of a passenger boarding bridge leveling mechanism may also move linearly as the passenger boarding bridge extends back and forth, the detection error may be avoided. Generally, a mechanism for realizing back and forth linear extension movement of the leveling wheel 15 needs to utilize a guide rail, a slider or a roller, however, in an actual use, because the aircraft fuselage represents a certain curvature, the mechanism with the linear extension movement has an upward or downward component force when the aircraft ascends or descends, which force tends to jam the linear extension movement or deform the guide rail, so that the mechanism is unreliable.
The above information disclosed in this background section is only intended to enhance understanding of the background of the present disclosure, and thus may include information that does not constitute the prior art known by those ordinary skilled in the art.